C5b-7 and C5b-8 precursors of the membrane attack complex (C5b-9) are effective killers of E. coli J5 during serum incubation

• Published in: Immunological investigations Vol. 26; no. 4; p. 409
• Main Authors: Bloch, E F, Knight, E M, Carmon, T, McDonald-Pinkett, S, Carter, J, Boomer, A, Ogunfusika, M, Petersen, M, Famakin, B, Aniagolu, J, Walker, J, Gant, R, Walters, C S, Gaither, T A
• Format: Journal Article
• Language: English
• Published: England 01.01.1997
• Subjects: Blood Bactericidal Activity; Colony Count, Microbial; Complement C5 - immunology; Complement C8 - deficiency; Complement Membrane Attack Complex - immunology; Complement System Proteins - immunology; Escherichia coli - immunology; Humans; In Vitro Techniques; Neutralization Tests
• ISSN: 0882-0139; 1532-4311
• DOI: 10.3109/08820139709022698

The finding that C9-deficient sera (C9D) can kill serum sensitive strains of Gram-negative bacteria by us and other investigators, questions the role of C9 in the membrane attack complex as necessary for cell death. In these studies we have demonstrated that C5b-8 complexes generated on E. coli J5 during incubation in C9-depleted and C9-neutralized sera are effective in killing Gram-negative bacteria. In the same study, we extended our investigations to show that the deposition of C5b-7 complexes (from C8-deficient [C8D], C8 depleted and C8-neutralized sera) is also effective in killing Gram-negative bacteria. In all cases, these studies demonstrated that when E. coli J5 was incubated with C8D, C9D and pooled normal human serum [PNHS], deposited C5b-9 complexes from PNHS produced more killing than C5b-7 or C5b-8 complexes alone. These experiments clearly demonstrated that C5b-7 and C5b-8 complexes are bactericidal and that multimeric C9 within C5b-9 is not an absolute requirement for inner membrane damage and cell death of Gram-negative bacteria.